Does mental exertion during incremental exercise change substrate oxidation and cardiorespiratory outcomes in individuals with overweight?

Given the growing concern over the impact of brain health in individuals with overweight, understanding how mental exertion (ME) during exercise affects substrate oxidation and cardiorespiratory outcomes is crucial. This study examines how ME impacts these outcomes during an incremental exercise test in adults with overweight. Seventeen adults who were overweight completed an incremental exercise test on a cycle ergometer two times, with and without the Stroop task. Energy expenditure (EE), carbohydrate and fat oxidation, maximum heart rate (HR_max), maximal oxygen uptake (VO2_max), maximum fat oxidation (MFO), and the intensity of exercise that elicited MFO (Fat_max) are measured by indirect calorimetry. ME did not change the EE, carbohydrate, and fat oxidation at any stages of the incremental test. However, ME resulted in significantly lower HR_max, VO2_max, and MFO (p < 0.01) and increased NASA-TLX scores but showed no change in Fat_max. These results show ME decreases the value of HR_max, VO2_max, and MFO during the incremental exercise test. Due to the increased mental workload demonstrated by the NASA-TLX test, adults with overweight are unable to complete the test to the same extent as they did in the test without ME according to maximal levels in this study.